I don't think Liv had any right to start shouting at some stranger in the street over her parenting skills. Things aren't always as they seem, my son is autistic and can throw some almighty strops and screaming/crying over the slightest thing and then I get the looks and stares off passers by who think he is naughty and I can't control him.
The mother could have been suffering with post natal depression or had been up all night every night with a baby/child that doesn't sleep and just lost it for a moment(I'm sure we've all been there once)
I would imagine seeing some stranger screaming and aggressivly pointing there finger at their mom would of upset the child alot more.
PARENTS HAVE A RIGHT TO DISCIPLINE THEIR CHILDREN AS THEY WISH AND NOT BE HARANGUED AND HUMILIATED BY PEOPLE THEY DO NOT KNOW.
QUITE OBVIOUSLY IF A CHILD WAS BEING PHYSICALLY AND CRUELLY ABUSED THAT WOULD BE A DIFFERENT MATTER BUT SOME SMALL CHILDREN CAN BE EXTRAORDINARILY DEFIANT AND BETTER SOME CROSS WORDS THAN COMPLETELY LOSING CONTROL AND HITTING THE CHILD.